Fluorinated oxetane derivatives and production process thereof

ABSTRACT

A process for preparing compounds of formula (I) comprising radical addition of RfI to 3-(allyloxy)methyl-3-alkyloxetane (1) wherein R is C 1-3  alkyl and Rf is C 1-18  linear or branched fluoroalkyl. The compounds of formula (I) are useful as intermediates for preparing various fluorine-containing functional materials.

TECHNICAL FIELD

[0001] The present invention relates to oxetane derivatives having afluorine-containing substituent on the side chain, and a productionprocess thereof. The oxetane derivatives having a fluorine-containingsubstituent on the side chain are useful as intermediates for preparingvarious fluorine-containing functional materials.

BACKGROUND ART

[0002] A known method for synthesizing3-fluoroalkoxymethyl-3-alkyloxetane is, for example, condensation of3-bromomethyl-3-methyloxetane using a fluoroalkyl alcohol and an alkali(Japanese Unexamined Patent Publication No. 500422/1999). However, thismethod requires the use of expensive 3-bromomethyl-3-methyloxetane. Inaddition, there are some cases in which fluoroalkyl alcohols are notavailable. Therefore, the development of a more general-purposesynthetic method has been desired.

DISCLOSURE OF THE INVENTION

[0003] An object of the present invention is to provide a process forpreparing 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane.

[0004] Another object is to provide precursors thereof, i.e.,3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane and3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane, and processes fortheir production.

[0005] The present inventors carried out experiments using the knowncompound 3-alkyl-3-(allyloxy)methyloxetane as a starting compound andfound that radical addition of fluorinated alkane iodide to thiscompound can produce3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane, which is animportant intermediate in the preparation of oxetane compounds having afluorine-containing substituent at the 3-position. The inventors furtherdiscovered that 3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane canbe converted into 3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane underbasic conditions, and that the resulting3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane can further be convertedinto 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane through a reductionreaction.

[0006] The features of the invention are shown in the following Scheme1:

[0007] wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branchedfluoroalkyl.

[0008] The compound of formula (II) usually consists mainly of a transisomer (E isomer) but may be a mixture of trans and cis isomers (E and Zisomers). In the invention, the compound of formula (II) is convertedinto the desired compound of formula (III) through the followingreduction reaction.

[0009] The C₁₋₃ alkyl represented by R is methyl, ethyl, n-propyl orisopropy, preferably methyl or ethyl, more preferably methyl.

[0010] Rf is a C₁₋₁₈ linear or branched fluoroalkyl group having atleast one fluorine atom. A greater number of fluorine atoms is morepreferable. Rf is preferably a C₁₋₁₈ linear or branched perfluoroalkylgroup such as (CF₂),CF₃ (wherein n is an integer of 0 to 17),perfluoroisopropyl, perfluoroisobutyl or perfluoro-t-butyl, morepreferably C₂₋₁₈ perfluoroalkyl.

[0011] In the three-step reaction of the invention, it is important tomaintain the reaction system under neutral or basic conditions not onlyduring the reaction but also during the post-treatment because theoxetane ring is cleaved under acidic conditions, resulting in a failureto provide the desired compound.

[0012] The invention makes a variety of fluorinated alkane iodidesavailable and thus enables the production of oxetane compounds havingthe desired fluorine-containing substituent on the side chain.

[0013] The starting compound of the invention,3-alkyl-3-(allyloxy)methyloxetane (1), can easily be prepared by knownmethods, such as a method for synthesizing3-(allyloxy)methyl-3-methyloxetane from 3-methyl-3-oxetanemethanol (J.Macromol. Sci.-Pure Appl. Chem. 2335, A34(1997)) and a method forsynthesizing 3-(allyloxy)methyl-3-methyloxetane from2-(allyloxy)methyl-2-methyl-1,3-propanediol (U.S. Pat. No. 2,924,607).

[0014] [Reaction Conditions for Step A]

[0015] In order to produce3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I), the inventorsused 3-alkyl-3-(allyloxy)methyloxetane (1) as a starting compound andtried to carry out an addition reaction in the presence of a radicalinitiator to add perfluoroalkyl iodide. As a result, it was found thatthis reaction proceeds to produce the desired product in good yield.Although the addition reaction of perfluoroalkyl iodide to an olefin inthe presence of a radical initiator was a well-known reaction (generaldescription: J. Fluorine Chem. 1, 93 (1999)), the addition ofperfluoroalkyl iodide to 3-alkyl-3-(allyloxy)methyloxetane was unknown.In this addition reaction, avoiding the cleavage of the oxetane ring isimportant to produce the desired product in good yield. For this reason,a reaction under acidic conditions is not desirable. Since hydrogeniodide is readily removed from the resulting3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane under basicconditions, basic conditions are not preferable except in the case thatit is desired to obtain compound (II) immediately after the radicaladdition.

[0016] In the radical addition reaction, radical initiators such asazobisisobutyronitrile, benzoyl peroxide and t-butyl 2-ethylperhexanoatecan be used or the reaction can be carried out by radical cleavage ofperfluoroalkyl iodide caused by irradiation with light such as by a highpressure mercury lamp.

[0017] Although Rfl can be reacted with3-alkyl-3-(allyloxy)methyloxetane (1) in any molar ratio, it ispreferable that Rfl be used in an amount of 1 to 5 moles per mole of3-alkyl-3-(allyloxy)methyloxetane (1). Although the amount of radicalinitiator used may vary depending on the kind of initiator, it isusually preferable that the initiator be used in an amount of 1 to 5mole % relative to 3-alkyl-3-(allyloxy)methyloxetane (1).

[0018] The reaction temperature is in the range of about 50° C. to 80°C. and the reaction time is about 1 to 6 hours. The reaction can beperformed in a solvent, for example, ethers such as diethyl ether andtetrahydrofuran, esters such as ethyl acetate, or aromatic hydrocarbonssuch as benzene and toluene.

[0019] [Reaction Conditions for Step B]

[0020] Next, a reaction to remove hydrogen iodide from3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I) proceedsreadily under basic conditions to produce3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane (II). In this reaction,any appropriate base can be used. Basic conditions which are too strong,however, are not preferable because the reaction further proceeds toremove hydrogen fluoride from3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane, giving a byproduct.Examples of useful bases include alkali metal hydroxides such as sodiumhydroxide and potassium hydroxide, and alkali metal carbonates orhydrogencarbonates such as sodium carbonate, potassium carbonate, sodiumhydrogencarbonate and potassium hydrogencarbonate. The base ispreferably used in an amount of about 1 to 2 moles per mole of thestarting 3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I). Thereaction is preferably carried out at about room temperature and thereaction time is about 0.5 to 2 hours.

[0021] [Reaction Conditions for Step C]

[0022] Next, 3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane (II) isreadily converted into 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane(III) in the presence of a hydrogenation catalyst. Examples of usefulhydrogenation catalysts include palladium/carbon powder,palladium/barium sulfate, platinum oxide and Raney nickel. The catalystcan be used, for example, in an amount of about 0.1 to 5 mass %,relative to the compound (II). Although the reaction proceedssatisfactorily at room temperature and atmospheric pressure, it is alsopossible to carry out the reaction with heating or under pressure. Thereaction time is about 1 to 8 hours. Since reductive cleavage of theoxetane ring may occur under highly reductive conditions, the reactionshould be carried out under conditions under which the oxetane ring isnot cleaved. Examples of useful solvents include ethers such astetrahydrofuran and dioxane, and alcohols such as methanol and ethanol.

[0023] [Reaction Conditions for Step D]

[0024] Another method for producing3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane (III) comprises reducing3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane (I) withoutperforming the reaction to remove hydrogen iodide. Such reductionmethods include hydrogenation using a reduction catalyst such aspalladium/carbon powder, palladium/barium sulfate, platinum oxide orRaney nickel, or methods using a chemical reducing agent such astributyltin hydride or lithium aluminum hydride. The reduction catalystcan be used, for example, in an amount of about 0.1 to 5 mass % relativeto compound (I). The chemical reducing agent can be used, for example,in an amount of about 25 to 200 mole % relative to compound (I). Thereaction temperature is in the range of about −78° C. to 40° C. and thereaction time is about 1 to 4 hours. The reaction can be carried out ina solvent such as tetrahydrofuran, dioxane or like ethers.

[0025] The compounds of formulas (I), (II) and (III) prepared by theproduction process of the invention are useful as intermediates forpreparing various fluorine-containing functional materials, such asresins and coating surface modifiers.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Examples are given below to illustrate the invention in moredetail, but it is to be understood that the invention is not limitedthereto.

[0027] In the Examples, 3 m stainless steel columns packed with SE-30were used in gas chromatography analysis, unless otherwise specified.NMR was measured with a Bruker 300 MHz spectrometer using chloroform-dlas a solvent.

REFERENCE EXAMPLE 1

[0028] Synthesis of 3-(allyloxy)methyl-3-methyloxetane

[0029] 3-methyl-3-oxetane methanol (20.4 g), 50% aqueous sodiumhydroxide solution (268 g), tetrabutylammonium chloride (2.8 g) andhexane (300 ml) were placed into a 500 ml flask and stirred at roomtemperature. After 19.4 g of allyl bromide was added dropwise, thereaction mixture was heated and refluxed for 2 hours. After completionof the reaction, the reaction mixture was filtered and separated intoaqueous and organic phases. The aqueous phase was extracted with ethylacetate and the extract was combined with the organic phase and washedwith water. The solvent was distilled off using an evaporator, giving17.2 g (61%) of product. The product was analyzed by gas chromatographyand the results showed that the desired3-(allyloxy)methyl-3-methyloxetane was obtained in a purity of 98%.Therefore, the product was used without purification for the followingreaction.

[0030]¹H-NMR: 1.31(s,3H), 3.50(s,2H), 4.00(d,2H), 4.33(d,2H),4.50(d,2H), 5.17(d,1H), 5.27(d,iH), 5.92(m,1H)

EXAMPLE 1

[0031] Radical Addition

[0032] 3-(allyloxy)methyl-3-methyloxetan (7.1 g), nonafluorobutyl iodide(51.9 g) and azobisisobutyronitrile (0.245 g) were placed into a 100 mlflask and stirred at room temperature. Then the reaction mixture washeated to 70° C. and maintained at that temperature for 1 hour.

[0033] After completion of the reaction, nonafluorobutyl iodide wasdistilled off using an evaporator, giving 22.2 g of product. The productwas analyzed by gas chromatography and the results showed that thedesired3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-iodoheptyloxy)methyl-3-methyloxetanewas obtained in a purity of 94%. Yield: 85%.

[0034]¹H-NMR 1.33(s,3H), 2.88(m,2H), 3.59(s,2H), 3.74(m,2H), 4.38(d,2H),4.41(m,1H), 4.52(d,2H)

[0035]¹⁹F-NMR −81.6 ppm(3F), −114.4(2F), −125.1(2F), −126.4(2F)

EXAMPLE 2

[0036] Removal of Hydrogen Iodide

[0037]3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-iodoheptoxy)methyl-3-methyloxetane(19.5 g) was placed into a 100 ml flask and stirred at room temperature.Then 25 ml of a methanol solution containing 4.2 g of potassiumhydroxide was added dropwise and stirred overnight. The reaction mixturewas filtered and washed with aqueous sodium thiosulfate solution andwater and then dried over magnesium sulfate. The obtained product (8.5g) was analyzed by gas chromatography and the results showed that thedesired3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-heptenyloxy)methyl-3-methyloxetane wasobtained in a purity of 93%. Yield: 59%.

[0038] The desired compound was obtained as a separable 78:22 (E:Z)mixture of geometric isomers. This mixture was separated by HPLC underthe following conditions:

[0039] HPLC Conditions

[0040] Column: Fluofix 120N (Φ4.6*150 mm, product of Neos Co., Ltd.)

[0041] Mobile phase: Acetonitrile/water

[0042] Detection: UV(210 nm)

[0043] E-isomer

[0044]¹H-NMR 1.27(s,3H), 3.50(s,2H), 4.14(m,2H), 4.33(d,2H), 4.46(d,2H),5.87(dt,1H), 6.43(m,1H)

[0045]¹⁹F-NMR −82.1 ppm(3F), −112.8(2F), −125.2(2F), −126.7(2F)

[0046] Z-Isomer

[0047]¹H-NMR 1.25(s,3H), 3.46(s,2H), 4.28(m,2H), 4.33(d,2H), 4.46(d,2H),5.55(dt,1H), 6.26(m,1H)

[0048]¹⁹F-NMR −82.1 ppm(3F), −112.8(2F), −125.5(2F), −126.7(2F)

EXAMPLE 3

[0049] Hydrogenation

[0050]3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-heptenyloxy)methyl-3-methyloxetane(7.2 g) and 5% palladium/carbon powder were placed into a 100 ml flaskand stirred at room temperature. After the flask was purged withnitrogen, hydrogen was circulated through the flask at about 60 ml/minfor 4 hours. Then the reaction mixture was filtered through a celitecolumn to remove the hydrogenation catalyst from the reaction solution.The obtained product (7.0 g) was analyzed by NMR and the results showedthat the desired3-(4,4,5,5,6,6,7,7,7-nonafluoro-2-heptyloxy)methyl-3-methyloxetane wasobtained in a purity of 95%. Yield: 95%.

[0051]¹H-NMR 1.33(s,3H), 1.78(m,2H), 2.19(m,2H), 3.50(m,2H), 3.59(s,2H),4.38(d,2H), 4.52(d,2H)

[0052]¹⁹F-NMR 81.6 ppm(3F), −114.4(2F), −125.1(2F), −126.4(2F)

INDUSTRIAL APPLICABILITY

[0053] According to the invention, the known compound3-alkyl-3-(allyloxy)methyloxetane is used as a starting compound and aradical addition reaction is carried out to add fluorinated alkaneiodide, thus giving3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane, which is animportant intermediate for oxetane compounds having afluorine-containing substituent at the 3-position. Further,3-(3-fluoroalkyl-2-iodopropoxy)methyl-3-alkyloxetane can be convertedunder basic conditions into3-(3-fluoroalkylallyloxy)methyl-3-alkyloxetane, which can further beconverted into 3-(3-fluoroalkylpropoxy)methyl-3-alkyloxetane through areduction reaction.

1. A process for preparing a compound of formula (I) comprising radicaladdition of RfI to 3-(allyloxy)methyl-3-alkyloxetane (1) wherein R isC₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.


2. A process for preparing a compound of formula (II) comprisingreacting the compound of formula (I) under basic conditions to removehydrogen iodide therefrom wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linearor branched fluoroalkyl.


3. A process for preparing a compound of formula (III) comprisinghydrogenating the compound of formula (II) in the presence of ahydrogenation catalyst wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear orbranched fluoroalkyl.


4. A process for preparing a compound of formula (III) comprisingreducing the compound of formula (I) in the presence of a reductioncatalyst or a reducing agent

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.5. A compound of the formula (I)

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.6. A compound of the formula (II)

wherein R is C₁₋₃ alkyl and Rf is C₁₋₁₈ linear or branched fluoroalkyl.